1. Field of the Invention
The present invention relates to a sanitary napkin suitable for nighttime use. More particularly, the invention relates to a sanitary napkin provided with rear flaps for widely covering a posterior part of the crotch and the buttocks.
2. Description of the Related Art
Sanitary napkins suitable for nighttime use are typically constructed to include an elongated main body and front fold-back flaps and rear flaps projecting outward from transversely opposite sides of the main body.
Japanese Unexamined Patent Publication No. 2001-95842 (Patent Publication 1) discloses a sanitary napkin, wherein a narrowest portion where the width of the napkin is smallest is disposed rearward of the fold-back flaps but forward of the rear flaps. The rear flaps are shaped such that the width of the napkin gradually increases rearward from the narrowest portion, reaches a widest portion, and gradually decreases from the widest portion to a rear end edge of the napkin. Here, the rear flaps have edges shaped arcuately to project transversely outward, and the widest portion is substantially at a longitudinal center of the rear flap.
On the skin-side surface of the sanitary napkin disclosed in Patent Publication 1, gathered cuffs are disposed to extend longitudinally at both sides of its longitudinal centerline. These gathered cuffs exhibit an elastic contractive force for longitudinal contraction and are allowed to rise from the skin-side surface due to the elastic contractive force. The gathered cuffs extend from a region located between the fold-back flaps to a region located between front halves of the rear flaps, wherein rear ends of the gathered cuffs are substantially at the same position as the widest portion.
In the sanitary napkin disclosed in Patent Publication 1, the rear flaps are aimed at eliminating worries about rearward leakage of liquid, and the gathered cuffs interposed between the wearer's skin and the skin-side surface of the sanitary napkin are aimed at further eliminating worries about leakage of liquid.
On the other hand, Japanese Unexamined Patent Publication No. 2002-330992 (Patent Publication 2) discloses a sanitary napkin, wherein front wings project outward from transversely opposite sides of a main body and larger rear-side wings, which are disposed rearward of the front wings, also project outward from the transversely opposite sides. The rear-sidewings have fold-back portions extending alongside the front wings.
When the sanitary napkin disclosed in Patent Publication 2 is to be put on, the front wings are folded back against and adhered to an outer surface of an undergarment at a crotch part thereof. Subsequently,the rear-side wings are placed on a lower part of a back body of the undergarment, wherein the fold-back portions projecting into leg openings of the undergarment are folded back against and adhered to the outer surface of the undergarment. Thus, the sanitary napkin can be put on along with the undergarment.
When the elongated sanitary napkin disclosed in Patent Publication 1 is applied to the wearer's body, the skin-side surface may contact the vaginal opening (menstrual blood discharging part) at a position between longitudinal centers of the front fold-back flaps and face the anus at a position near the narrowest portion. Here, the rear flaps, which are placed on a lower part of a back body of an undergarment, may be curved to conform to the surface shape of the wearer's buttocks. Moreover, the rear flaps located rearward of the anus-facing portion may not project into leg openings of the undergarment.
In the sanitary napkin disclosed in Patent Publication 1, however, the rear flap has the arcuate edge over its entire length, wherein the widest portion is substantially at the same position as the longitudinal center of the rear flap and at a considerable distance rearward from the fold-back flap. Furthermore, the rear flap has a width gradually increasing from the narrowest portion behind the fold-back flap to the widest portion. That is, the front portion of the rear flap is of a small area.
In such a front portion of the rear flap, heretofore, it has been difficult to dispose a pressure-sensitive adhesive layer for adhering the rear flap to an undergarment; in the conventional sanitary napkins, therefore, the pressure-sensitive adhesive layer has been disposed only centrally of the rear flap.
When the sanitary napkin is worn, however, central and rear portions of the sanitary napkin subjected to a tightening force of the undergarment try to fit in the cleft of the buttocks, so that the front portions of the rear flaps tend to move away from the undergarment due to deformation of liquid absorbent layer. In addition, the front portions of the rear flaps tend to be drawn toward the cleft of the buttocks in conjunction with the deformation of liquid absorbent layer.
If the front portions of the rear flaps tend to move freely, as set forth above, the gathered cuffs inside them tend to come closer to the longitudinal centerline, substantially decreasing an area of the skin-side surface between these gathered cuffs. If the gathered cuffs fall inward, additionally, the exposed area of the skin-side surface will be much smaller. Accordingly, menstrual blood trying to flow from the anus to the buttocks may be directly given not only to the skin-side surface but also to the gathered cuffs. Moreover, the menstrual blood may easily migrate to the small front portions of the rear flaps beyond the gathered cuffs, flowing out of the front portions to reach the undergarment.
When a wearer lies on her back during sleep, on the other hand, the rear portion of the sanitary napkin may be flattened by the buttocks, so that a portion located between the front portions of the rear flaps may easily move away from the wearer's body with a bending force concentrated therein. At this portion, accordingly, the gathered cuffs need be raised high. However, since the front portions of the rear flaps are allowed to move freely at both sides of this portion as set forth above, the gather cuffs tend to come closer to the center. Furthermore, such high gathered cuffs tend to fall to cover the skin-side surface. As a result, menstrual blood can easily reach the undergarment beyond the front portions of the rear flaps, as set forth above.
Compared with the sanitary napkin disclosed Patent Publication 1, the sanitary napkin disclosed in Patent Publication 2 can be firmly fixed to the undergarment due to the presence of the fold-back portions of the rear-side wings. In this sanitary napkin, however, since four separate portions (the front wings and the fold-back portions of the rear-side wings) need be folded back against and adhered to the outer surface of the undergarment, the sanitary napkin will be troublesome to put on. In addition, it is difficult to hold the sanitary napkin in proper position with respect to the crotch part of the undergarment until the fixing procedure is completed. Furthermore, once the fixing procedure is completed, it will be extremely troublesome to change the position of the sanitary napkin.